Ionization energy is defined as the energy needed to extract one mole of electrons from one mole of gaseous atoms. Factors influencing ionization energy include nuclear charge, electron-nucleus distance, and inner electron shielding.
- Across a period (left to right): Ionization energy increases with nuclear charge. Atomic size diminishes, drawing electrons closer to the nucleus and increasing removal difficulty.
- Down a group (top to bottom): Ionization energy decreases due to increased atomic size and shielding effect. Outer electrons are more distant and experience greater repulsion from inner electrons, facilitating their removal.
Element analysis:
- Lithium (Li): Atomic number 3, Group 1, Period 2. Possesses a low first ionization energy due to a single, distant outer electron easily removed.
- Sodium (Na): Group 1, Period 3. Exhibits a lower ionization energy than lithium as its outer electron is further from the nucleus.
- Neon (Ne): Group 18, Period 2. A noble gas with a stable electron configuration. Demonstrates the highest first ionization energy because its electrons are tightly bound due to a complete octet.
- Magnesium (Mg): Group 2, Period 3. Has a higher ionization energy than sodium but lower than neon. This is attributed to its position in the same period as sodium but with an additional proton in the nucleus.
Conclusion: Neon (Ne) exhibits the highest first ionization energy.